GRAND FORKS - A "significant severe weather outbreak" will likely hit eastern North Dakota this afternoon and hang around until Wednesday morning in northwestern Minnesota, the National Weather Service says.
Some thunderstorms are already moving into the Red River Valley this morning. Those will diminish, and as solar heating creates warm and humid conditions, more thunderstorms will start to develop early this afternoon, starting in the Devils Lake basin and central North Dakota and entering the valley late this afternoon and evening, said Geoff Grochocinski, meteorologist at the weather service office in Grand Forks.
"Tornadoes are possible, but I think the biggest threats are just large hail and damaging straight-line winds," he said.
Areas of heavy rainfall and localized flash flooding also are possible.
The culprit is an unusually strong upper-level low pressure center for this time of year that's moving eastward across southwestern Canada, near the international border. The strong directional turning of winds in the lower portion of the atmosphere will allow rotating supercell thunderstorms to develop with the potential to form tornadoes, according to a weather service statement.
"It looks like we'll definitely get something in the area today," Grochocinski said.
The system is expected to hang on tonight and linger with thunderstorms east of the valley through tomorrow morning, he said.